The present invention relates to a paper feeding device to be used in a recording apparatus such as an electrophotographic copier or the like and particularly to a paper feeding device wherein a paper is fed with a bottom plate in the paper feeding cassette on which recording papers (sheet paper) are loaded, and which is lifted up each time a paper is fed.
As is well known, in many of the paper feeding devices for electrophotographic copying machines or the like, papers are loaded on the bottom plate in the paper feeding cassette, the bottom plate is lifted to a paper feeding member such as a paper feeding roller, and the paper feeding is performed by function of the paper feeding member.
In a paper feeding device of this type, it is necessary to release a member for lifting the bottom plate from the paper feeding cassette when the paper feeding cassette is inserted or extracted from a paper feeding stand. In the past, therefore, a manually-operated lever that can control the posture of the lifting member has been provided with the paper feeding stand and the manual operation of said lever release the lifting member from the paper feeding cassette. Alternatively, a cam that controls the posture of the lifting member has been provided on one side of the paper feeding cassette and thereby the lifting member is pulled in temporarily inside of the paper feeding stand from the inside of the cassette when the paper feeding cassette is inserted or extracted. With the former structure, however, extremely troublesome operations are needed because the manually-operated lever must be operated each time the paper feeding cassette is inserted or extracted. With the latter structure, on the other hand, there has been a problem that an insertion or an extraction of the paper feeding cassette is not easy because a considerable resistance is applied on the paper feeding cassette when it is inserted or extracted.
Therefore, previously, the inventor of the present invention proposed a paper feeding device with a structure wherein the bottom plate of the paper feeding cassette is lifted only when the paper feeding operation is made, in U.S. patent application Ser. No. 386,624 (filed on June 9, 1982). Namely, in the paper feeding device, the lifting member energized by a spring is locked in a non-operation position by a deterring member, and the escape of the deterring member and the rotation start of the paper feeding member (a paper feeding roller) are made by a clutch such as an electromagnetic clutch or the like incorporated in the power system. However, the above paper feeding device, though it has a merit that the insertion and the extraction of the paper feeding cassette can be made smoothly without any manual operation, has drawbacks that the spring to energize the lifting member tends to become fatigued since it is always kept in the loaded condition and an expensive electromagnetic clutch or the like is needed.